This invention relates to remotely releasable joints for interconnecting pile members or other tubular elements, and to methods of making and breaking such joints.
When piling is driven into an ocean floor to anchor a marine drilling platform to the floor, it is customary to ultimately remove some of the upper `follower piles` from each string of piling after the driving operation has been completed. To enable such detachment of a follower pile from a permanent pile, connections have been devised which are intended to be rigid enough to withstand the forces encountered during driving of a string of piling into the earth, but which can be relatively easily released after the driving operation is completed to permit an upper portion of the string of piling to be retreived. For use in situations in which the connection to be released is accessible at the surface of the water, or near the surface by a diver, the joint may be designed for disconnection by a wrench or other manually actuated tool. In some instances, however, a joint between a permanent pile and a follower pile may be just above the ocean floor and so deep as to render its direct access to a diver difficult if not impossible. For use in such situations, special connections have been proposed which can be located near the ocean floor but which can be released remotely from the surface of the water. For example U.S. Pat. No. 4,074,912 issued Feb. 21, 1978 to Bilderbeek et al. shows a connection which is adapted to be released remotely by lowering a releasing tool through a follower pile and to a location at which it can engage and withdraw upwardly a retaining sleeve within the connection. This sleeve holds a series of connecting fingers of the joint structure in a locked position until upward removal of the sleeve frees those fingers for radially inward movement in a manner enabling the upper portion of the string of piling to be withdrawn upwardly. It is our understanding that this type connection has not proven as satisfactory as would be desired in use, and is subject to possible unintentional release by displacement of the retaining sleeve during the pile driving or other handling operations. Another expedient which has been utilized is a `breech block` type of connector, having interrupted thread like projections which are designed to enable the connection to be made or broken by rotation of one pile member relative to another. Such breech block connectors are shown for example in U.S. Pat. Nos. 3,421,580, 3,442,536, 3,800,869, 3,974,875, 4,165,891, 4,185,856 and 4,209,191. This type of remotely releasable connector has the disadvantage of requiring provision of equipment at the surface of the water which is capable of turning the upper portion of the string of piling, with resultant increase in cost and inconvenience of the pile handling process.